A wide variety of different types of container exist for the packing and shipping of goods. These range from paper envelopes and wooden crates to custom plastic and metal enclosures. However, very few of these containers can protect contents from extreme temperatures greater than 1000° F. over meaningful time durations such as three hours or more.
Many situations can arise where protection of contents from extreme heat is needed. A fire in a cargo hold generates ample temperatures to require this type of protection. One example of growing importance is the shipment of lithium batteries and lithium-ion batteries (herein referred to generically as “lithium batteries”). Lithium batteries can be dangerous under some conditions and can pose a safety hazard because they contain a flammable electrolyte and also because they are kept pressurized. Moreover lithium batteries contain oxidizers, which can makes fire suppression very difficult.
Accident investigators recently traced a fire that destroyed a UPS Boeing 747 in the United Arab Emirates city of Dubai in 2010 to lithium batteries being carried in the cargo hold. Investigators emphasized that the crash highlighted the risks posed by shipment of lithium batteries, which are prone to overheating, leading to intense fires. Unless something is done to prevent similar disasters, the FAA now says such crashes are all but inevitable in the future.
In the wake of the Dubai 747 crash, UPS has started using fireproof cargo containers, and has ordered more than 1,800 fiber-reinforced shipping containers that are designed to withstand fires for up to four hours. However, while such containers may maintain their integrity in a fire, they do little to prevent a surrounding fire from heating lithium batteries contained therein and eventually causing them to explode.
It is estimated that over a billion lithium cells are flown each year. In a recent report issued by the Federal Aviation Administration in conjunction with Transport Canada, the agencies predicted there will be an average of six cargo plane crashes between now and 2021, with four of them likely to be caused by lithium battery fires.
The US Department of Transportation (“DOT”) has specified that dangerous materials when shipped must not become accelerants or contribute to a fire in airplane cargo holds. The US DOT criteria require that there be no contribution to the fire from shipped materials for 3.5 hours when exposed to a temperature of 1000 F.
Some postal administrations currently restrict air shipping (including Emergency Medical Systems) of lithium and lithium-ion batteries, either separately or installed in equipment. Lithium-ion batteries containing more than 25 grams (0.88 oz) equivalent lithium content (“ELC”) are forbidden in US air travel. Similar restrictions apply in Hong Kong, Australia and Japan.
One approach to reducing the risk of lithium battery explosions during a fire is to enclose the batteries in so-called “phase-change” packaging, which is packaging that surrounds contents with an unbroken barrier comprising an substance such as water that vaporizes when subjected to heat, thereby maintaining the contents at the boiling temperature of the vaporizing substance until the vaporizing substance is exhausted. Unfortunately, however, many phase change packaging approaches that work well at less extreme temperatures fail when subjected to temperatures greater than 1000° F. This is because internal structural degradation caused by the very high temperatures tends to open up gaps or “windows” in the phase change shield that allow the external heat to penetrate and reach the inner contents. Even if the phase change substance is contained in compartments or “packs” of a gel or similar substance, and the packs are held in place by rigid walls that maintain their structure at high temperatures, the packs themselves can nevertheless shrink and sag as the water or other phase-changing substance is consumed, thereby opening up gaps or “windows” in the phase-change shield.
Some of these limitations can be avoided by filling a packing container with a mixture of vermiculite and water as a single-use packing material that completely surrounds and submerges the lithium batteries or other contents. When heated, the water in the vermiculite is vaporized, but the vermiculite continues to surround and cover the contents, allowing the vaporized water to flow throughout and permeate the vermiculite, so that “windows” are avoided and the contents remain protected until the water is fully exhausted. However, while somewhat effective, such packaging requires added insulation, is not easy to use, is not reusable, and is not sufficiently robust or durable for certain applications.
What is needed, therefore, is a robust, durable, easy to use, reusable container capable of protecting contents from surrounding high temperatures up to 1000 degrees Fahrenheit for a minimum of at least three and a half hours.